Generally, a positioner in a medical imaging apparatus is used for positioning patients for medical imaging. Examples of a positioner include a patient support table, a vascular gantry comprising a C-arm and a pivot, etc. Examples of a medical imaging apparatus include an X-ray apparatus, a CT scanner, a vascular imaging apparatus, etc.
Typically, the positioner includes a positioner unit and a drive mechanism comprising one or more drive motors for driving the positioner unit along various positioner axes such as, longitudinal, lift and tilt axes. A brake is coupled to the drive mechanism for holding the positioner unit in desired state for positioning a patient for medical imaging. Examples of a positioner unit include a patient cradle in a patient support table, a C-arm and a pivot in a vascular gantry.
However, movement of the positioner unit along the positioner axes such as, for example, lift axis in a vascular gantry, longitudinal axis (in tilted position) in a patient support table, is susceptible to influence of gravity. Moreover, during circumstances such as malfunction in the drive motor, power failure, etc, these axes require a proper braking system for preventing uncontrolled movement of the positioner unit and hence enable safe positioning of the patient for medical imaging.
Known braking systems for a positioner in a medical imaging apparatus include a rotary brake coupled to a drive mechanism corresponding to the positioner axis susceptible to influence of gravity. For example, in the patient support table, the rotary brake is coupled to a shaft of a drive pinion configured to mesh with a rack coupled to a guide mechanism of the patient cradle.
However, during drive along a positioner axis that is susceptible to influence of gravity, if a failure such as a single point failure arises at a location beyond the connection point of the brake and the shaft of the drive pinion, then the operation of the rotary brake does not result in stoppage of patient cradle movement because of the influence of gravity. One example of a single point failure includes teeth breakage in the drive pinion. Thus, conventional braking systems do not allow for sufficiently safe patient positioning for medical imaging, as uncontrolled movement of the positioner unit under the influence of gravity may result in improper patient positioning and may also cause injury to patients during positioning operation.
Thus, there exists a need in the art for a sufficiently safe braking system that would not allow uncontrolled movement of the positioner unit under the influence of gravity, especially during a failure such as, a mechanical failure in the drive mechanism corresponding to a positioner axis that is susceptible to influence of gravity.